Oddsocks

Hi Tom. Not quite sure what you are doing here, you can't cut the end off a standard USB cable and connect it directly via a RG11 to the RS232 port on the MESU. Windows will never recognise the MESU as a RS232 port, the USB port hardware on the host computer will only recognise and configure standard USB devices. You must use a USB-to-RS232 port emulator/adaptor and connect the emulator/adaptor to the MESU. Something like this, preferably using a FTDI UART chip with COM retention, USB-to-RS232 emulator: https://www.amazon.co.uk/StarTech-com-USB-Serial-Adapter-Powered/dp/B004ZMYTYC/ref=sr_1_1?ie=UTF8&qid=1549930141&sr=8-1&keywords=1+port+ftdi+usb+to+serial+rs232+adapter+cable+with+com+retention You will also need a re-wireable DB9 connector, with shrouds, to connect the RS232 emulator/adaptor cable to the RJ11 plug. https://www.amazon.co.uk/Serial-Connector-Removable-Plastic-Housing/dp/B00KDBXD3W/ref=sr_1_fkmr1_1?ie=UTF8&qid=1549930766&sr=8-1-fkmr1&keywords=rewireable+db9+female I've linked to a Startech RS232 emulator/adaptor above as these were the make I used to use at work and proved reliable, though expensive. You can find cheaper makes that use FTDI UART's but avoid Prolific UART's there are so many fake Prolific UART chipped devices out there and many prove unreliable. The latest FTDI UARTS use COM port retention so once Windows has recognised it and registered the COM port even if you move the USB plug to a different USB socket on the computer the port number in software does not change. HTH William. *EDIT* Note, see appendix D of the Sitech manual (page 47) for wiring diagram of the RS232 port DB9 plug to Sitech RJ11 plug, also, you do not require or connect the 5V pin, only RX, TX and 0v are used.

Thank you for the kind comments Alan. I think you can probably tell I spent too much of my youth watching Blue Peter! ?

Hello Jamie. As described above in Alans reply, @symmetal, the contour maps are produced by specialist software however this would not be of much use to you in this case because they map the entire optical chain of the telescope as well as the light source and with a large aperture OTA such as the C9.25 you won’t be able to move the entire OTA over the face of the light box to determine the evenness of light distribution without overlapping the edge of the light box and producing an inaccurate result. Happily there is a simple solution using your ZWO ASI 1600 camera by converting it into a temporary photometer. Remove the camera from the telescope and if not already fitted then attach the standard camera 2” nosepiece. Using a piece of aluminium kitchen foil, temporarily wrap the foil over the nosepiece so that it lies flat across the nosepiece aperture. Make a 1mm diameter pin hole in the foil in the centre of the nosepiece aperture. Carefully slide the foil off the nosepiece then cut a couple of pieces of white printer paper into small disks or squares for use as a diffuser/attenuator, approx 1cm x 1cm, shape doesn’t really matter, and glue or tape the paper disks (or squares) across the pinhole on the inside of the foil as a double thickness. Reattach the foil to the nosepiece and secure with tape or rubber bands. Reinforce the foil with a couple of strips of transparent sticky tape across the face ensuring that the pin hole is roughly centred to a piece of the tape and not lying across the edge of the tape (to avoid diffraction effects). The camera can now be used as a crude but accurate and effective photometer. Place the camera nosepiece in close, direct contact with the surface diffuser of the flat panel, somewhere near the centre of the panel, ensure the flat panel has been switched on for at least fifteen minutes to allow it to stabilise, darken the room to avoid stray light affecting the measurements and then take an image with the camera. Adjust the camera exposure time to achieve an average ADU for the entire image of approximately half max value (saturation) then using the same exposure time simply move the camera across the face of the flat panel in a rough grid pattern, 1cm steps would be sufficient, make a note of the camera average ADU reading at each sample grid point as you move the camera over the flat panel and then plot the resulting readings. What you have constructed could be described as a 'spot' photometer and it's sample area is very small, dictated by the size of the pinhole in the foil. Measurements made with a spot photometer can be adversely affected by small defects in the surface of the flat panel diffuser which, when used as a light source for the telescope would not be noticeable as the light source is so far out of focus. You could enlarge the size of the pinhole and add additional paper attenuators to the inside of the foil to increase the sample area size however you would achieve better results by converting the 'spot' photometer into an 'area' photometer by moving the surface of the foil/camera away from the face of the flat panel diffuser. To do this simply measure the length of the camera nosepiece and cut a cardboard tube approximately 1cm longer from the inside of a roll of toilet paper or kitchen paper (or simply 'roll your own') and slide it over the nosepiece so that the foil face and pinhole is now sitting inside the tube to a depth of 1cm. Now when you hold the camera against the flat panel the pinhole being further from the panel will be sampling a larger area, depending on the geometry of the camera probably ~5mm to ~10mm diameter, which will even out the small imperfections in the flat panel diffuser and give you a more meaningful measurement. When used as an area photometer it would be good practice to blacken the face of the aluminium foil that looks towards the flat panel to prevent over illumination due to internal reflections between the face of the flat panel diffuser and the foil, it probably won't make a lot of difference when used for this task as the inaccuracies due to the reflections will be the same across all the measurements however if you wanted to improve the accuracy of the photometer you could blacken the foil, or place a blackened cardboard aperture mask across the face of the foil, use a different material for the foil such as thick opaque black plastic etc, just depends what materials you have to hand. Your capture program should be able to display image stats like max/min and average ADU pixel values and using the camera as a photometer in this way the average ADU would be sufficient. If your capture program does not display image stats then there are several free image processsing programs and FITS viewers available that can show this information. A well made EL panel would typically show a variation of less than ~1% average ADU across it’s illuminated surface, a LED draughting panel rather more, up to 5% is not unusual, even for a very well made panel. If your flat panel shows a variation of less than 5% ADU across the field then it should be adequate. HTH. William.

Tom. If I remember correctly RS485 uses differential amplifiers in the transceivers for the RX and TX signals so Rx has it’s own separate 0v and Tx has it own 0v, they can’t share a common 0v on the signal pairs. The Sitech is RS232 and RS232 uses end-to-end cabling and doesn’t use differential amps so you only need three wires, Rx, Tx and a common 0v (and maybe +5v if the receiver amp in the device is not host powered). Besides the above, the logic levels are different with RS232 working at either 5v or 15v and RS485 working at 6v, finally, RS232 uses simplex or full duplex modes and RS485 only uses simplex or half duplex. Bottom line is that in very few cases can RS485 be directly substituted for RS232 unless the port hardware is either user or auto detect configurable and the full set of cabling is provided. Looking at the Sitech drawings and manual this appears to be an RS232 only device. HTH. William.

The EPDM is certainly easier James. The flat, low-profile corrugated steel panels look better and probably last longer but installation on a ridged roof is complicated unless you can get all the components needed from the same manufacturer. We re-roofed the scout hut with metal panels two years ago, previously it was felted but vandals set the roof on fire and we thought metal was less of a liability. We had to cancel the TP order though when we found they didn't stock the ridge caps and barge boards. One of the scout assistants knew somebody in the trade and we bought enough 1.6mm thick sheets in blue to cover the 4m x 6m hut, with matching barge boards, ridge caps, and corrugation meshes, and got free delivery, from a company in the Midlands. I seem to recall the final bill was around £500 though. My neighbour has re-roofed his garage with TP panels in grey but that is a flat roof with just a six degree fall so no need for ridge caps and the barge boards are all treated timber plus he didn't need to cut any of the panels so a much easier job. William.

Hello James. There are ~five Travis Perkins depots within twelve miles of you that can deliver plastic-coated galvanised-steel low profile sheet roofing panels in two colours, grey or green, and three lengths, i’ve linked below to the shortest length they do in green. https://www.travisperkins.co.uk/Steel-Roof-Sheet-BS12B29-Juniper-Green-Plastic-Coated-Sheet-6ft-(1825mm)/p/766965 The only issue with TP is they don't stock and are unable to supply the matching ridge cap and barge board panels so you have to find a solution that works for you for the ridge cap, I don’t know why TP don’t supply these, we did email them several times but answer came there none! No wonder TP are always in some kind of financial mess. Things they don’t tell you in the technical specs: The panels expand and contract a large amount with temperature change and when the panels are nailed or screwed to the roof only the first fixing hole at the top of the sheet should be a tight fit on the shank of the fixing, all the holes below it should be drilled oversize, at least twice the diameter of the fixing shank, so that the panel can move as it heats up, otherwise the thin panel will warp and lift and never sit flat on the roof. If you have to cut the panels to length the cut ends should be painted with a flexible sealant, such as bitumen or a silicone rubber as even though the steel is galvanised before coating it will gradually rust inwards from the cut and delaminate, the cut ends should be hidden under the ridge cap or under overlapping sheets when used on long spans. When used on a battened roof you can’t walk across the panels, the TP ones are too thin and will crease, the panels used in commmercial builds are much thicker and stronger. The TP panels are ok to walk on when laid directly on a supporting board. The open ends of the corrugations at the eaves and at the ridge need closing with a mesh so that wasps can’t set up home in the corrugation voids but there is still some ventilation under the panels. The grey coloured panels are better at keeping cool, the green ones look good but get very hot, both are better than black rubber or felt though for helping keep the inside of the building cool, especially if you use mesh guards at the corrugation openings rather than foam inserts to maintain airflow. HTH William.

Even worse this morning Grant. Unable to load any page on iMac from home fast fibre, takes around four minutes to load on an iPad if Safari doesn’t give up and time out first. William

A European alternative to Precise Parts is TS in Germany, they offer a range of adaptors to your specification, Sonder65 to Sonder125 ~65 EUR to 125 EUR (Sonder in German = Special in English). https://www.teleskop-express.de/shop/index.php/cat/c123_Adapter-to-other-Threads.html Less expensive than the Precise Parts equivalent as there are no import duties though you would probably have to finish the TS adaptor by hand painting internally, the Precise Parts adaptors are both black anodised and painted internally with anti-reflective matt-black paint, the TS adaptors are only black anodised and therefore remain quite reflective to certain wavelengths of light. If you email a sketch drawing of the adaptor you want built, including thread diameters, length of thread and thread pitch to TS they will quote you a price.

Depends how much you are willing to pay and what length of focal path you have to play with Mark. The shortest length that I found possible uses 8.8mm of focal path and that would be a custom adaptor from Precise Parts in the USA. I have used them in the past and they are well made and fairly quick to ship, usually three to five weeks from order to delivery. A suitable custom adaptor would be ~$112, plus shipping, plus VAT, and plus duty when it lands in the UK. If you use their 'Build-an-Adaptor' service on their web site you will see a 3d representation of the part and it's cost. I don't know the make of OAG you have so in the 'Build-an-Adaptor' I used Skywatcher Esprit 120/150ED flattener for the M62 Female side and Hotech 2" M48 Field flattener for the male side to give the m48 male thread (obviously you wouldn't be connecting two flatteners together but this generates an adaptor with the right threads and minimum focal path). If you know the make and model of OAG you have you might find it is already listed in the Precise Parts 'Build-an-Adaptor" database, if not, there are many other possibilities to try that have 2" M48 threads. https://www.preciseparts.com/ppmain/adapter.html Otherwise, I think FLO have, or did have, an engineer that could make adaptors and other engineering parts to order. William.

Looking at the side-by-side image you posted, all the donuts in the master flat have concentric bright rings around them. I thought at first that this might be just a bit of jpeg-ery edge detection enhancement going on with the screen capture but the fact you see these artefacts in the calibrated light suggests it is a real artefact in the flats. Posted screen captures are really much too low quality here on the SGL forum to make an accurate diagnosis and it is always a good idea to post the fits images as well, or a link to a Dropbox or Google Drive folder containing them when asking for help with image artefact or calibration issues. Taking your screen capture and applying curves in PS shows that the darker donuts in the flat master are also present in the calibrated lights, it is not just the bright arc that remains after calibration. There are only two ways to produce bright concentric ring artefacts in the flat masters (using PI) that I am familiar with. First is a change in focus during the time it took to take the flats, i.e, the telescope focus was not consistent across the full sequence of flats used to create the master. Second, either bias frames were not taken and included in the batch processing script (or if using the manual calibration tool in PI, a bias master was included but the tick box 'calibrate' was not ticked in flats selection window), or there is a temperature mismatch between the lights, darks, flats and bias frames, and/or a matching dark frame for the flats was not included in the batch processing script. Because both the bright ring and the dark donuts are present in the calibrated image then it confirms the flat is not calibrated correctly. In PI when calibrating images from a 8300 sensor it is essential that the full set of matching temperature calibration frames are included, if the flats exposure is longer than a few seconds, then matching time and temperature darks are also recommended. If it is simple case that you did not take bias frames, or matching time dark frames for the flats, set the camera to the same temperature as for the lights and take a series of bias frames and matching time flat-dark frames now and rerun the batch processing script with the bias and flat-darks included, that should fix the bright ring artefacts around the dark donuts in the flats and calibrate the lights correctly, if it doesn't, try the manual calibration tool instead as I find it often produces better results than the batch processing tool as you have more control over the fine-tuning characteristics of the calibration procedure. If you did take bias frames and flat-darks and include them in the batch processing script or manual calibration tool check the fits headers for the bias, darks, flats and lights, were they all taken at the same temperature? If these images were taken with the G2-8300 the 8300 chip shows a great variation in dark current with temperature so it is important the temperature is consistent across all the frames used (as I found out with my own QSI 683 that uses the same sensor). I can't offer a post processing solution to fix your current image but maybe going back over the calibration procedure with the full set of matching calibration frames will solve the problem and you won't need to resort to "air-brushing" the final image. HTH.

You are welcome Shahd, I'm happy I was able to suggest a possible answer to the problem and that you did't waste time retaking the luminance and calibration frames unnecessarily. Thank you for the kind comments Olly. When diagnostic imaging (medical) was my career I found the professionals I used to support appreciated an explanation for the problems they might be seeing with their equipment rather than just a blanket response that told them nothing as some of my colleagues tended to do. Some of my bosses over the years used to complain that I never sent e-mails, only novella! I do try to include as much as I can in as few words as possible but as you know it isn't easy! You are too kind Wim, I do appreciate your comments and trying not to blush. The post was written in rather a hurry and looking back now I would have changed the sentence structure and shortened it a bit to make it easier to read, there's always room for improvement! William.

Whenever you see ‘Bas Relief’ effects (3D) in subtracted or divided images this is almost always due to mechanical movement between the two source images, in this case the images are the flat master, or flat stack and the target image stack. DBE has detected and enhanced the image artefacts resulting from mechanical differences beween the master flat and image stack. The dark areas around the galaxies is most likely due to poor placement of the sample points in DBE/ABE Most likely there was some physical movement of the L filter, camera, flattener, focuser etc, either during the flats acquisition or the lights acquisition and this may have affected the entire series of flats, or lights, or just a few individual subs in either stack. Since you report that RGB were ok but only L was affected I would suspect the filter wheel maybe was knocked during the sequence, possibly the L filter is loose in its holder or the wheel detent is a bit loose in the L postion allowing some movement as the telescope assumes different positions for flats and target imaging, or possibly the flattener to filter wheel coupling is a little loose, even slight focuser movement can cause these effects. The artefacts are quite large making me think these are dust particles further up the image chain than the filters. You can measure the donuts in the image and determine how far from the sensor the dust particles are and that will give you a better idea of what moved, filter or coupling between filter wheel and flattener, focuser, OTA etc using the formula: D=Pdf Where D= the distance from the sensor to the dust casting the shadow, P=The width of the dust donut in pixels, d=The width of a single pixel and f=The focal ratio of the telescope. If you use the pixel size in millimetres then the distance will be in millimetres too, if you use pixel size in microns the distance will be in microns so you just need to be able to convert accordingly. Once you have the distance calculated you can work out what moved. HTH.

Check the following two images for a possible answer to your problem. Screen shots are from Photoshop CS6 on a Mac. This is how to enable/disable automatic hands free execution of an Action: First image, in the Actions list there is a selectable button to the left of the Action name, this is called the Dialogue button, when this button is selected and 'lit' then the Action will proceed step by step and pause where it requires you to interact in some way followed by an ‘OK’ to continue. (*See footnote below*) To run an Action without manual interaction select the Action title and not the Dialogue button to the left of its name, if you do accidentally toggle the Dialogue button so it is lit just toggle it again. The box must be dark for the action to run ‘Hands Free'. Second image shows the Actions menu. Click the menu icon at the top right of the Actions tab to open the Actions Menu. Click 'Playback' options. Choose 'Accelerated'... for fastest automatic execution or choose, 'Step-by-Step'... to watch each individual step in an action execute, optionally, define a fixed pause time for each step by selecting 'Pause For'. For each of these Playback options as long as the dialogue button to the left of the Action title is not lit then the Action sequence will run automatically without user interaction and will follow these option choices. If the dialogue button to the left of the Action title is lit then none of these options will have any effect and the Action sequence will proceed Step-by-Step requiring each step to be acknowledged with an ok. H.T.H. *Note: Some Actions do require user input to achieve the best results since they are optimised for a particular 'starting state' of the image, which your image may not meet. Unlike some dedicated astronomy image processing programs Photoshop does not evaluate an image to determine image characteristics and adjust processing parameters to suit the image, you need to manually adjust tool settings used for some Action steps to suit your image. To see which steps in an Action normally require user input first toggle the Dialogue button to 'on' (lit) then expand the Action by clicking on the right-arrow immediately to the left of the Action title and scroll down the list of Action steps. Any individual Action step that has the Dialogue button 'lit' would normally be a point where you need to make an adjustment to a setting so that you get the best out of that step. If you wish, you can choose individual steps in an Action to not require user interaction while leaving other steps that do by disabling the Dialogue button associated with that individual step. When you do this the Dialogue button next to the Action title will change to include a short horizontal bar in the centre of the box, this is notifying you that something has been changed from the way the original Action was created. To restore the Action to the way it was originally written click on the Dialogue button immediately to the left of the Action name and the bar through the centre of the Dialogue button will disappear indicating that the Action has been returned to it's original configuration. If you decide to run an Action fully hands free, with the Dialogue button next to the Action title deselected (dark) then you almost certainly will not get the best results from the action. An action should really be thought of as a set of regularised procedures rather than as automatic image processing.*

Yes, convert to 16bit using Mode before anything else. When you select an action is the dialogue button to the left of the Action name selected and lit? If the button is 'lit' then the Action will pause at each step in the action sequence and prompt you for an ok, at least this is my experience running Astronomy Tools Action set in Photoshop CS6 for Mac. To run an action automatically just click on an Action title while making sure the dialogue button to the left of the title remains dark, if it is 'lit' click on it to toggle it off then press the 'play' button at the bottom of the Actions tab. See following post for pictures and explanations.

Were these working at one time for you and have now changed behaviour? I don’t know about Annie’s actions but Astronomy Tools action set only works properly with 8 or 16 bit images, I’ve been caught out a few times importing 32bit images and trying unsucessfully to run actions on them. If you import a 32bit image you have to convert it to 16bit mode before attempting to run actions. One other issue I have noticed several times is that if you open an individual action and toggle the tick boxes for any step in an action a warning message will appear saying what you are about to do may not be reversable, continue, Yes / No?, or words to that effect, if you go ahead and toggle the step then sure enough the action will stop at that point and wait for you to respond to an ok prompt however going back to that step and toggling the selection box back to how it was does not reset the action, it will always stop at the same point again and wait for you to ok. The only way I have found to fix this is to delete the entire action set and reinstall it.

I am not a PHD user and don't know the software that well but there is interesting information in the log window, statistics box shows RA RMS was 97.19 pixels against DEC RMS of 1.79 pixels, graph shows clearly periodic error but the scale is too large in the posted image to be able to see the guiding corrections and Luke reports the stars are trailed in the RA direction. To me that suggests that PHD is locked to the guide star but no guiding corrections are being issued to the mount. Luke's PA is good so no drift in DEC but no mount corrections would cause star deformation in RA direction due to PE and gradual drift over time in RA due to mount tolerances/ belt mod/wrong RA rate set, etc etc. To fault find further and as already noted above I think you would need to set up normally take a series with guiding enabled and then immediately after another series with guiding disabled. If there is no difference between the two series that would indicate that for some reason PHD guiding corrections are not being issued to the mount even though PHD is locked to the guide star. Other than that you could go into ASCOM diagnostics and enable logging then read the log after a guiding session to see if guiding corrections are being sent to the mount (assuming you are using ASCOM guiding of some kind). The PHD guiding log can be read like a normal text file and it may show the guide star's centroid position throughout the run, if the x and y centroid position is the same at the end of the run as it was at the beginning but the main camera image is drifting then that would indicate either flexure, rotation, or the guide camera image is not being updated. Depending which capture software you use in some software packages you can configure storage of the guide camera images along with the main camera images, a quick comparison of the start and end run images from both cameras would confirm flexure or rotation, if the guide camera images show no drift but the main camera does then = flexure or rotation, if drift is seen in both guide camera and main camera images then guide corrections are not being sent to the mount. How far off axis is the guide telescope compared to the main telescope? is the guide star selected in the same frame as the main camera? A big differential and a little polar misalignment would create drift due to rotation.

There are two possibilities that I can think of: 1: Capacitively trapped electrons in the rows and columns closest to the left side and bottom edge of the array where there are, depending on the particular deign of detector, a number of "dark" rows and columns used for on-chip dark calibration, these are covered by a vapour deposition metal plate a few atoms thick and the plate could, in theory, form one pole of a capacitor. 2: Beyond the dark rows and columns are the row and column amplifiers that are a source of IR. The amount of IR emitted is a constant since the read time of the row and column amplifiers (and therefore their "on" time) never varies irrespective of individual exposure time and would be a source of low level read noise added to every exposure. The IR, depending on source intensity, can only penetrate so far into the wafer. Without knowing the actual structure of the detector, which would be a design secret, it is not possible to say which of the above is the most likely, the irregular shape of the "glow" hints at a capacitive trapped electron theory but depending on the layout of the row and column amplifiers the leaked IR from the row and column amplifiers is just as likely. One test you could do is to flood the detector with light and read the array with a single exposure and then immediately cover the detector and take a dark bias, if the edge glow changes after the flood exposure then that would hint at the trapped electrons explanation since flooding the detector will dislodge some of them, if the edge glow is exactly the same after the flood exposure then that would hint at IR from the row and column amplifiers as being the source. You might find the linked document of interest: https://courses.cs.washington.edu/courses/cse467/08au/pdfs/lectures/07-cmos-ccd-imagers.pdf

You are more than welcome, makes a change for a question to be asked that I know a little about. I would change the battery as soon as possible and not risk leaving it until it stops working, this design of battery was never meant for the consumer market and has special characteristics that make it difficult to handle. The electrolyte is highly reactive with water and although the battery case is stainless steel the case seals are known to deteriorate over time and once they fail and water vapour contained in normal air enters the battery a violent reaction occurs that causes the case to swell up and split, the contents are highly corrosive (lithium salt) and often the battery will split, leak its contents over the circuit board they are attached to and within a few hours the board will be destroyed. Although very rare for a genuine traceable battery from a good manufacturer, I have known these batteries to suffer seal failure, swell and split, less than a month after fitting. Ten years is about the maximum predicted mechanical life once the battery is installed and in use. Lithium Thionyl Chloride is highly toxic as well and has to be disposed of as hazardous material. When you change the battery take care not to short it out while removing the old one and fitting the new one, although they are low current batteries and can only provide approx 30 to 40 mA this is sufficient to cause the battery to explode if the short remains for long enough. You can find further information about the chemistry of this battery at the following Wikipedia page and looking down the list for the chemical formula LI-SOCl2 (IEC Code: E) https://en.wikipedia.org/wiki/Lithium_battery#Chemistries

The battery type ER6V/3.6V is an industry standard "AA" Lithium Thionyl Chloride data backup battery and it is not rechargeable. There are rechargeable Lithium batterys but these use a different chemical composition and construction technology, known as Lithium Ion, they have a high internal leakage current and are unsuitable for data backup since they need recharging every few months, they also may have a different terminal voltage to the type fitted to your handset, typically 3.7V to 3.85V Your handset will only work correctly with the standard, non-rechargeable ER6V/3.6V "AA" Lithium Thionyl Chloride battery and the most common makes are Toshiba, Saft, Varta and Tadiran with power ratings of around 2000mAh to 2600mAh, these should last around ten years in storage and five to eight years in use, depending on storage temperature and equipment use, the longer the handset is powered up and in use the longer before the backup battery needs replacing. Toshiba sold their battery business quite a few years ago and I don't know where the Toshiba branded batteries are coming from now. Be careful where you buy the battery from, there are a lot of counterfeit fakes around, especially on internet auction sites, the counterfeits are known to leak, catch fire or explode, if in doubt it is better to pay a higher price to buy one from a trustworthy supplier. I used to fit the Varta made ER6 AA type to medical systems here in the UK and we bought ours from RS because of the guaranteed supply chain, you have to check the solder tab orientation and layout though. Some solder tab batteries have a right angle, large, single tab at one end of the battery and a right angle, small, double tab at the other, some have axial tabs, some have axial solder leads or opposing tabs etc but all the variants should have the standard "AA" battery style body, ~50mm long and ~14.8mm diameter. RS stock all the typical solder tab types, about twenty five variants last time I looked, you just need to search for 3.6V AA lithium non-rechargeable and you should find them all, linked below are the most common types I last used, any of the types linked below with the correct solder tab arrangement will be suitable. http://uk.rs-online.com/web/p/aa-batteries/7020815/ http://uk.rs-online.com/web/p/aa-batteries/7781153/ http://uk.rs-online.com/web/p/aa-batteries/7781150/ http://uk.rs-online.com/web/p/aa-batteries/6684553/ http://uk.rs-online.com/web/p/aa-batteries/7020818/ HTH.

Thanks Gav. Had a great summer travelling and on the last few days staying with the partners in laws in Switzerland, supposed to be out sailing today but tipping down so just reading eating and drinking today! Will be home this weekend and then the fun starts getting to grips with ACP and setting up the Paramount MX sky model PEC and polar alignment, reckon that will take me a month (at least). Best of luck with your dome old_eyes. Only other tip I can give re a concrete pad if you go that way is to make sure the surface is properly sealed before the dome is installed otherwise the sealant they use around the base will not stick, I was lucky that the builders were watching out for me while away and they found lots of water inside the dome one morning after the sealant had peeled away from the dusty concrete pad, the builders lifted the dome in one piece and sealed the concrete with Ronseal Concrete Sealant, which is a solvent based acrylic polymer that penetrates deeply into the concrete slab and dries in a few hours, then they lowered the observatory back onto the pad and redid the silicone rubber sealant, that was back in May and since then it has remained dry.

Having worked with industrial high voltage power supplies in medical systems, up to 200 kV, in often damp operating theatre environments I'm all too aware of the dangers of dampness and electricity! I did my own installation but not being domestic qualified I still had to have it certified by council building control. Power out to the dome was by buried armoured two core, live and neutral only, with a two metre earth rod at the dome and the cable armour grounded at the house supply end only, insulated at the dome end. All dome earthing is via the grounding rod including the steel pier. Consumer unit, light, light switch and sockets all IP66 waterproof rated, consumer unit and sockets all individually RCD protected, overkill really but I already had the RCD protected sockets for another cancelled job. The Pulsar dome has an inward fitting dome-wall flange so it is just possible for some rain water drips to be blown inside the dome as well as condensation drips from the dome roof to track down the to the dome-wall flange so it is not a good idea to mount a consumer unit directly on the wall as any drips from the flange may fall on it. My Pulsar dome has a single bay and if you have a bay you could fix the consumer unit inside the bay on the flat wall, but I wanted my bay free for computer and networking so I mounted my consumer unit, three double sockets, twin network ports and earth distribution box all on a piece of varnished 3/4 ply 1 mtr tall and around 300mm wide. The plywood panel is screwed to a block of wood on the floor set 60mm away from the wall, there is a stand-off wood block screwed to the dome wall flange-web three quarters of the height of the wall. Difficult to visualize but imagine a free standing plank set away from the wall and screwed to a wood block on the the floor with a single wood block supporting the plank near the top. This means no screw holes in the dome exterior wall just a single bolt hole internally where each wall segment meets its neighbour and forms an internal webing joint. By standing a panel inside the dome any dripping water from the dome-wall flange falls to the ground behind the panel and being a flat surface the consumer unit and sockets are simple to fit. The panel was transferred from my old Skyshed POD and attached are a couple of pictures from when it was installed there, the only change being the stand-off support is nearer the top of the panel in the Pulsar and in the Skyshed the stand-off is fixed to one of the POD wall through bolts, in the Pulsar it is fixed directly to the turned-in wall web where the individual wall panels meet. The pictures were taken before the network cables were terminated so are just seen looping out of the surface mount box, in the Pulsar these are now neatly terminated.

I had Pulsar dome installed this Spring on a concrete base, the Observatory has not been used through the Summer due to travelling but is being commissioned now so no real data yet on thermal cooldown rates but if you look at professional observatories of the last few hundred years they are built on concrete or brick and not on decking! The key is good ventillation. There were some condensation problems initially with my Pulsar dome and builders carrying out restoration work on my home while I was away fitted a solar powered stainless-steel ships yacht's extractor fan in the southern wall, this runs all day and contains a small rechargeable battery that keeps the fan running for an hour after sundown. On an observing night the shutter and entry door would be opened at the onset of twilight and imaging or observing won't begin for at least another hour and this should be sufficient to allow most thermals to diminish to a negligible level. During the day the vast mass of concrete, base and pier block, are shaded from direct sun being inside the observatory so the concrete mass will be closer to average ambient then say a concrete path or roadway that would sit in full sun all day. Once the observatory is open and the pad begins to cool the rate of heat transfer would be quite low, concrete is not a great thermal conductor and with a low transfer rate thermals set up inside the observatory should not really be that great. Last couple of points regarding a concrete base, you won't be leaving the floor inside the observatory plain concrete, not a good idea, expensive gear does get dropped and it wont bounce on concrete! Most have some kind of floor covering and the interlocking 10mm thick foam rubber tiles that many use both insulate the floor against thermal transfer from concrete pad to inside dome as well as providing excellent protection against damage to falling items. If you do go for a concrete base then if possible design it to be no bigger than 150mm wider than the dome to keep the unshaded concrete to a minimum and also to minimise the area that standing water can accumulate, good drainage is essential all round the dome to prevent water creeping under the dome walls. I made my concrete pad octagonal being a bit lazy and not wanting to spend ages on the shuttering for the concrete pour but I think the the bases made with circular shuttering look really neat and meet the requirement of minimum exposed concrete to sun and standing water Regarding decking I can be more certain since my previous Skyshed Pod was on decking and it was a continual problem with water leaks, rotting timbers, insect infestation as well as the occasional rat or mouse problem. Decking really is meant for sitting on in removable chairs etc, it does not like things left on top of it as water will collect under said objects and in no time begin to rot the decking. With decking, the timbers expand and contract a huge ammount with the seasons, properly installed, a gap of several millimeters is left between each decking plank and it's neigbour to allow for seasonal expansion, this gap is a good route for water to track below the dome walls and start to rot the timber within a few months of fitting. Decking timbers are probably the cheapest low grade "flooring" you can get, it is certainly not allowed for internal house construction, cut from the tree heartwood after all the good stuff is removed for other purposes it often has tightly radiused end grain which means the planks warp width-ways and continually move as the moisture content changes through the year. Any extenal silicone sealant used to seal the observatory base to the timber decking is continually pulled away from the joint by this timber movement so you will be chasing leaks. Inside the observatory the gaps between the planks allow free movement of creepy-crawlies as well as high water vapour movement from the ground below and the space below the decking is a great place for a rats nest. Any timbers that do warp or rot badly will need the observatory jacking up so that the plank can be extracted and replaced which means the entire observatory timber-dome seal has to be cut away and redone. If you try to install a water barrier sheet above the decking and below any internal dome flooring this just allows the decking timbers to become sodden with condensed vapour from the ground and if you place the barrier sheet between the decking beams and planks this just does the same to the beams, seems you just can't win. There is no doubt that a small dome looks good on decking but as a practical proposition I found it a continual headache and given my experience decking would not even be a serious proposition. HTH. William.

Yes, that value is quite plausible. In the first document I linked to: ( http://www.astropixel.gr/uploads/7/8/3/5/7835053/scientifically_determining_ccd_gain_and_offset.pdf ) the authors tested their QHY9M and determined their gain as 17% with an offset of 112 so your current settings of 19% and 110 are not that far away but remember these numbers though very small have a big effect on the way the camera records the image and to get the best out of the camera you need to measure and set the gain and offset accurately.

You can copy from someone else but the offset and gain values they use will only apply to your camera if the factory QA was observed exactly for each camera assembled and that there has been no calibration drift caused by ageing components in your camera since it left the factory.

This document explains the steps to take, bit lengthy but easy to follow: http://www.astropixel.gr/uploads/7/8/3/5/7835053/scientifically_determining_ccd_gain_and_offset.pdf Also a Craig Stark blog which is a general description of the offset and gain functions: http://www.stark-labs.com/help/blog/files/GainAndOffset.php William.